Producing dental replacement parts like crowns and bridges requires the exact determination of the dental situation in the mouth of the patient. Otherwise, the dental replacement parts will not accurately fit.
For determining the dental situation in the mouth of a patient different methods are know. Besides imaging and computer based methods, a huge portion of this task is still accomplished by using conventional dental impression materials.
Dental impression materials can be classified according to their curing mechanism (e.g. addition curing or condensation curing). Dental impression materials can also be classified according to their consistency. Besides low viscous dental impression materials, there exists highly viscous, so-called putty like dental impression materials.
Dental impression materials are typically provided as two component systems which consist of a base and a catalyst paste and which are mixed before use.
Due to its high viscosity, mixing putty like dental impression materials with an automated system like the Pentamix™ device (3M ESPE) can be difficult. Thus, often putty like dental impression materials are mixed (i.e. kneaded) by hand.
The materials are typically pasty and cure in the mouth of the patient due to a chemical curing mechanism. The cured material is removed from the mouth of the patient and the obtained impression represents a negative image of the dental situation. The impression is then typically filled with plaster to obtain a positive model. The positive model is used for designing the desired dental replacement part.
However, for capturing the surface details of the subgingival regions of the hard dental tissue, i.e. the region below the gum line, conducting a dental retraction process is typically needed. Capturing those surface details is important if a dental replacement part is desired, which fits well to the surface of the prepared tooth. Currently, different kinds of retraction processes and materials are known.
Many dentists still use dental retraction cords, which are placed in the sulcus of the tooth, remain there for a sufficient period of time and are removed later before conducting the impression process.
Alternatively, a dental retraction material can be used, which is inserted into the sulcus, kept there for a sufficient period of time and which is removed, as well, before the impression process is conducted.
In order to function as dental retraction material, the material has to have a certain stiffness or viscosity, which allows the retraction material to keep the sulcus open (withstand sulcus pressure).
A commercially available dental retraction material is e.g. provided by 3M ESPE under the brand 3M™ ESPE™ Retraction Capsule or 3M™ ESPE™ Astringent Retraction Paste, respectively.
In contrast to dental retraction materials, a dental impression material has to show good flowing properties and has typically a thin consistency. Conducting such a separate retraction step is time consuming. Patients and dentists nowadays have an increasing demand for a simplified method for taking dental impressions.
WO 2012/177985 A2 (Dentsply) relates to a tissue management impression material and a method of application into the sulcus of a patient, whereby the tissue management impression material is a part of the final dental impression made when manufacturing a dental device, such as a crown.
US 2012/0045732 A1 (Chen et al.) describes a dental paste dispensing device having a modified dispensing end for atraumatic contact with soft tissue.
US 2011/0046262 A1 (Bublewitz et al.) describes pasty masses that are suitable as insert material for widening the gingival sulcus. The materials described contain a paste-forming agent, superabsorber particles and at least one astringent.
US 2014/050043 A1 (Durali et al.) relates to a universal dental impression material system using a programmable device having containers for separately housing two or more components that form a dental impression material when mixed.
US 2014/0170596 A1 (Angeletakis) describes a two part retraction system than can be inserted into the sulcus to form a semi-rigid porous elastomer releasing a hemostatic agent suitable for sulcus retraction such that a dental impression may be completed by a dental practitioner.
U.S. Pat. No. 4,468,202 (Cohen) describes a method of obtaining a dental impression comprising the steps of retracting gingival tissue by applying a photocurable or chemical curable elastomeric material into the space between the teeth and the gingival tissue, curing the elastomeric material to a certain degree, applying a second photocurable or chemically curable elastomeric material in contact with the subgingivally applied elastomeric material, curing the elastomeric material to a certain degree and removing the cured elastomeric composite. It is described that the two elastomeric materials are contained in containers separated from each other, from which the material may be selectively expelled.